What Everest Teaches About Disease

Researchers are going to great lengths-or rather, great heights-to further their understanding of the heart, lungs and brain. Shirley Wang explains on Lunch Break. Photo: Mayo Clinic.

By

Shirley S. Wang

Updated May 29, 2012 1:47 p.m. ET

Researchers are going to great lengths—or rather, great heights—to further their understanding of the heart, lungs and brain.

A team of Mayo Clinic scientists recently accompanied climbers to Mount Everest to study the effects of high altitude. And researchers from the University of Colorado, Denver, are planning a high-altitude research trip to Bolivia with 24 study participants.

At high altitudes, the body's main challenge is dealing with low oxygen levels in blood or tissue, as well as lesser stresses involving diet, fluid, temperature and UV exposure.

For four weeks starting April 20, Mayo Clinic researchers were in Nepal taking physiological measurements of 10 climbers' hearts and lungs, as well as conducting sleep studies and cognitive performance tests on them.

The climbers spent six weeks at base camp, elevation 17,500 feet. The researchers, arriving from Rochester, Minn., elevation 1,300 feet, conducted the same assessments on themselves to compare results of those who had acclimatized with those who hadn't, says Bruce Johnson, Mayo professor of physiology and medicine who led the research. The expedition was sponsored by National Geographic and apparel maker the North Face, with support from Montana State University.

By studying the climbers, six of whom reached the summit, the researchers hope to gain insight into heart failure, lung disease and sleep apnea—all conditions related to a low-oxygen, or hypoxic, state. The longer people spend at extreme high altitude, the longer their bodies lack the needed amount of oxygen and the lower their energy—stresses similar to those caused by the diseases.

Conditions on Everest have been especially difficult this year because of the less-than-usual amount of snow and ice on the ground for climbers to dig into. There have been greater numbers of climbers at high camps waiting to attempt the summit, Dr. Johnson says. A high-altitude bottleneck of climbers played a role in the deaths of four climbers descending the summit earlier in May.

The proportion of oxygen in the air—21%—is constant whether at sea level or on the highest peak, but at lower altitudes there is more air pressure to force oxygen into tissue. At higher altitudes, where atmospheric pressure is lower, oxygen enters the body less readily, leading to the hypoxic state.

The bodies of most healthy people will adjust to an hypoxic state, up to a point, with changes in the blood, such as an increase in oxygen-transporting molecules called hemoglobin, as well as in the brain and muscle.

A better understanding of such changes could eventually lead to drugs that could artificially induce acclimatization and help with heart and lung diseases that limit oxygen levels in the body, says Robert Roach, director of the University of Colorado's Altitude Research Center. "If we could trigger acclimatization, those patients could gain exercise capacity and suffer less from their disease."

The research also might lead to new ways of controlling the body's response to low oxygen in other contexts, such as one day helping limit growth of certain solid-tumor cancers, which need oxygen and blood vessels to grow, Dr. Roach says.

Altitude research already benefits patients with medical conditions and vice versa. Asthma inhalers like albuterol, which work by stimulating beta-receptor cells in the lungs, were first used to treat high-altitude climbers. Conversely, several heart-failure medicines are now in use to treat altitude sickness or help with acclimatization, researchers say.

The researchers hope to find out what happens to fluid in the lung at high altitudes. Lung congestion is a problem in patients with heart failure, when the heart isn't able to pump enough oxygenated blood to other organs, Dr. Johnson says.

Back in Minnesota, complementary studies are examining the role of hypoxia in heart failure and the mechanisms involved. "These are small steps along the way to a bigger path," Dr. Johnson says.

The team also is focusing on why climbers at high altitude experience poor sleep. Most heart-failure patients also develop periods of broken sleep, known as central sleep apnea. Analyzing data from studies conducted on Everest, the researchers intend to examine what happens to oxygen levels during sleep and how that may contribute to sleep disturbances, Dr. Johnson says.

The University of Colorado researchers are studying molecular mechanisms of normal acclimatization in healthy people to gain new treatment ideas for people with chronic obstructive pulmonary disease, or COPD, a common lung disease.

Currently, the group is in Oregon testing 24 healthy volunteers at sea level. Starting July 12, they will test the same participants at Bolivia's Mount Chacaltaya, at 17,200 feet.

Of great interest is the physiological pathway called the hypoxia-inducible factor, or HIF, which seems to trigger the body's response to low-oxygen levels in tissue. At high altitude, the body's main response is to breathe a lot, in an effort to pump more oxygen to muscles, brain and wound-healing processes; with continued low oxygen, muscles begin to waste away, appetite is suppressed and exercise capacity is reduced, Dr. Roach says. People with COPD experience these same symptoms.

The researchers hope their work may lead to a COPD treatment that mimics the adjustments of a healthy body to an oxygen-depleted state. "We strongly believe if we can identify molecular pathways controlling healthy response to low oxygen, we can develop new ideas for treating COPD," Dr. Roach says.

Science in Extreme Conditions: the Mayo Clinic's Bruce Johnson

Bruce Johnson, a recreational climber, has spent part of his career studying cardiovascular disease and part studying human performance in extreme environments. A native of Salinas, Calif., Dr. Johnson, 54, runs the Mayo Clinic's Human Integrative and Environmental Physiology Laboratory, which studies the limits on human performance in heart and lung diseases.

ENLARGE

Bruce Johnson, at base camp on Everest in Nepal in 2012
Mayo Clinic

In his doctoral work at the University of Wisconsin, Madison, he studied factors limiting performance in elite runners. Afterward, he went to Mayo to study fatigue, and never left.

In his 15 years at Mayo, he has investigated apnea in divers in Croatia and conducted several research projects on mountain peaks including Argentina's Mount Aconcagua. He also spent two seasons several years ago in Antarctica.

'As much as I like the adventure and fancy myself as still somewhat athletic, we are pretty much now focused on our research work and the training up of young scientists,' Dr. Johnson says.

Dr. Johnson says whether due to extreme altitude or heart failure, low oxygen in the blood or tissue results in similar bodily changes, which may include:

Stimulation of breathing and the sympathetic nervous system, which governs the fight-or-flight response

This copy is for your personal, non-commercial use only. Distribution and use of this material are governed by our Subscriber Agreement and by copyright law. For non-personal use or to order multiple copies, please contact Dow Jones Reprints at 1-800-843-0008 or visit www.djreprints.com.